1. Field of the Invention
This invention relates to machine tools and, more particularly, to a machine tool having a spindle headstock that cooperates with a tool turret assembly in processing workpieces.
2. Background Art
In the machine tool industry, one common machine tool configuration employs two independent machining assemblies, each having a spindle headstock and one or more tool turret assemblies. Essentially, these designs function in certain respects as to two independent machining units to provide the required system flexibility and efficiency. Variations have been introduced into the industry to make these systems even more efficient and flexible. Generally, these improved systems incorporate additional components which make more complex the coordination of movement of system components to provide the desired efficiency and flexibility without interference and potential collision between the components.
An exemplary prior art machining system, over which the present invention improves, is shown at 160 in FIG. 12. The machining system 160 consists of a support 162 upon which the system components are mounted. The system components consist of a first spindle headstock 164, a second spindle headstock 166, a first tool turret assembly 168, and a second tool turret assembly 170. The first spindle headstock 164 includes a spindle 172 which is rotatable around a central axis 174. The spindle 172 is capable of chucking a workpiece and rotating the same around the central axis 174. The second spindle headstock 166 likewise has a spindle 176 to chuck a workpiece and rotate the same around a central axis 178 for the second spindle headstock 166.
The first tool turret assembly 168 consists of a first turret headstock 180 to which a first turret head 182 is mounted for pivoting around an axis 184. The second tool turret assembly consists of a second turret headstock 186 which mounts a second turret head 188 for pivoting movement about an axis 190. The first and second turret heads 182, 188 each carry a plurality of tool holders/tools that can be selectively indexed to an operative/active position.
The second spindle headstock 166 is fixed to the support 162. The first spindle headstock 164 is translatable selectively oppositely along a first line, parallel to a Z-coordinate axis and an orthogonal second line, parallel to an X-coordinate axis, as indicated by the double-headed arrows 192, 194, respectively. Similar movement is allowed along the first and second lines, as indicated by the double-headed arrows 196, 198 for the first tool turret assembly 168, with like arrows 200, 202 indicating the same translatory movement for the second tool turret assembly 170.
The spindles headstocks 164, 166 face towards each other, with the former facing in a first direction. Because the spindles 172, 176 are movable towards each other along the first line/Z-axis, it is possible to compact the system along the first line/Z axis. The first and second turret heads 182, 198 face opposite to the first direction along the first line, as indicated by the arrow 204. With this arrangement, the first and second turret heads 182, 188 can be advanced along the first line/Z-axis opposite to the first direction, as indicated by the arrow 204, towards the spindle 172.
With the machining system 160, outer diameter machining can be performed on a workpiece chucked by the spindle 176 by tools held by one or both of the first and second turret heads 182, 188.
Additionally, backside processing can be performed on a workpiece chucked by the spindle 172 at the same time front side processing is performed on a workpiece held by the spindle 176, using separate tools held by the first and second turret heads 182, 188.
Additionally, after finishing the front side processing of a workpiece held by the spindle 176, the same workpiece can be transferred to the spindle 172 to allow performance of backside processing thereon. This potentially shortens the overall processing cycle.
Because of the absence of a tool turret assembly in association with the first spindle headstock 164, inside diameter processing utilizing the advancing movement of this turret assembly cannot be performed on either a workpiece chucked by the spindle 176 or a workpiece chucked by the spindle 172.
Additionally, center axis chattering may be caused by a center-holding subspindle which center supports the front side of a workpiece which is chucked by the spindle 172. This introduces the need for another tool turret assembly in association with the first spindle headstock 164. This can be accomplished by incorporating a third tool turret assembly (not shown) that is capable of moving along the first line/Z-axis, and second line/X-axis independently of the first spindle headstock 164.
However, incorporating an independent third spindle assembly, as described above, potentially introduces significantly increased costs and may result in a complicated mechanical system with potentially complicated and difficult coordination of movement between the multiple components.